diff --git a/src/InvalidPostcodeException.php b/src/InvalidPostcodeException.php
index 629f70c..c3785ec 100644
--- a/src/InvalidPostcodeException.php
+++ b/src/InvalidPostcodeException.php
@@ -7,6 +7,6 @@
 /**
  * Exception thrown when trying to format an invalid postcode.
  */
-class InvalidPostcodeException extends \Exception
+class InvalidPostcodeException extends \Exception implements PostcodeException
 {
 }
diff --git a/src/PostcodeException.php b/src/PostcodeException.php
new file mode 100644
index 0000000..e1dc5f3
--- /dev/null
+++ b/src/PostcodeException.php
@@ -0,0 +1,9 @@
+<?php
+declare(strict_types=1);
+
+namespace Brick\Postcode;
+
+interface PostcodeException extends \Throwable
+{
+
+}
\ No newline at end of file
diff --git a/src/UnknownCountryException.php b/src/UnknownCountryException.php
index 47cfdd5..bc8a475 100644
--- a/src/UnknownCountryException.php
+++ b/src/UnknownCountryException.php
@@ -7,6 +7,6 @@
 /**
  * Exception thrown when an unknown country code is provided.
  */
-class UnknownCountryException extends \Exception
+class UnknownCountryException extends \Exception implements PostcodeException
 {
 }